Apple has released a chess program for the ipod (5th gen or classic or new video nano)  it can be downloaded to itunes and placed on your ipod for only $5.00.  It also has a backgammon game as part of the program though I have little interest in backgammon.  There are 9 levels (monkey to master)  graphics are good, but it does have a number of drawbacks.  First in 2D mode, the mode I prefer to play in, you can't flip the board - black is always at the top.  More seriously it has problems calling a draw.  It seems to be confused over the 50 move rule, so that if you don't get a checkmate in 50 moves from the start of the game (rather than the last capture or pawn move) it will declare a draw.  Also it can only save the game currently played so you can't review past games.  On the plus side it as a quiz mode which can be kind of fun - it has you find forks/pin/mates in 2 etc.  However many of these positions are not ones you would see in regular play so they are far inferior to the tactics trainer on this website.  Overall this program has a number of drawbacks, (the worst of which will hopefully be patched) but for a mere $5.00 is worthwhile if you have already shelled out the bucks for an ipod. 

Hmm.  I have an itunes gift card, perhaps I will use some of that on this.  Although I already have a Kasparov Chess for my cell phone, which is pretty challenging for me, so far the best I've done is draw against intermediate.

its the same with all cheap games